JP2590033B2 - Multilayer blow molded container - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a multi-layer blow-molded container made of plastic, and more particularly, to a multi-layer blow-molded container provided with a joint formed by pinch-off at the bottom thereof, wherein each of the same layers of a multi-layer structure is joined at the joint. Are substantially continuous, and the advantages of the multilayer structure, for example, oxygen permeation resistance, moisture resistance, organic solvent resistance, chemical resistance, mechanical strength, etc., are also excellent at the pinch-off joint. It concerns a container.

[0002]

2. Description of the Related Art It has been known that a multilayer molded container having a plastic multilayer structure is excellent as a container having the unique characteristics of each layer. However, a multilayer molded container having a joint formed by pinch-off at the bottom is known. In the blow-molded container, the same layers of the multilayer structure are connected to each other at the joint, and the oxygen-permeable property, which is an advantage of the multilayer structure at the joint,
There have been difficulties in the production of containers and containers that maintain moisture resistance, organic solvent resistance, chemical resistance, mechanical strength, and the like. There have been various proposals for this type of container and its manufacturing method, but regarding the present invention, in particular, Patent Application Publication No. 53-15432 and Patent Application Publication No. 59-11
The technique described in Japanese Patent No. 5234 can be cited as a conventional technique.

[0003] The container described in the former publication and a method for producing the container are characterized by an inner and outer surface layer made of a polyolefin known per se,
Similarly, a bottom pinch-off joint of a tubular parison having a container wall composed of an intermediate layer having a specific oxygen barrier property known per se as a ridge having a tapered portion projecting outward from the container wall known per se. Forming, in the joint portion, the same layers are substantially continuous with each other in plane,
Although it is recognized that the combination is patentable with its combination, the pinch-off joint is, for example, V-shaped,
It has the greatest feature in that it is formed in a tapered shape such as U-shaped, semi-circular, semi-elliptical, Mt. Fuji, or a combination of U and V to connect the same layers to each other. In the shape, it is excluded that the same layers are not continuous with each other, and the reason has not been elucidated.However, the reason for this is that if a split groove having a tapered portion is used, the ridges in the pinch-off portion of the bottom of the container are used. The pressure starts to be applied first from the narrowest part of the cross-sectional width of the container, and the thickness of the outer layer of the container that is in contact with the split mold is larger than the width of the tapered part of the split mold. It is said that the company considers that there is no external exposure of the intermediate layer that would affect the performance of the container.

[0004] The multilayer container described in the latter publication has a multi-layer parison in which at least two or more layers of a main layer such as polyolefin and a gas-permeable layer such as saponified ethylene-vinyl acetate copolymer are laminated. In a multilayer container formed by forming a rib in a pinch-off portion formed by sandwiching the multilayer parison by a mold by sandwiching and molding by a mold,
Both side surfaces of the rib are inclined so as to expand from the base end toward the tip, and the width of the tip is 1.1 to 5 times the width of the base end.
The height of the rib is set to be 0.5 to 5 times the width of the base end. The description is limited only to the dimensional ratio of the rib shape, and the layer configuration of the container wall is referred to. However, the dimensions of the ribs relative to the thickness of the container wall are not particularly described.

[0005]

According to the description of the above-mentioned Patent Application Publication No. 53-15432, a pinch-off joint is formed, for example, in a V-shape, a U-shape, a semicircular shape, a semi-elliptical shape,
It is said that the same layers can be connected to each other by forming an arbitrary tapered shape such as a Mt. Fuji type or a combination of U and V, and the same layers are not continuous in a planar shape or a rectangular shape.
According to an experiment conducted by the inventor when necessary, it is difficult to completely connect the same layers with each other if the pinch-off junction is formed in a tapered shape, unlike the description in the publication. However, when the pinch-off joint is formed in a rectangular shape having a narrowed portion at the base of the protruding portion, although it has a specific size relative to the wall thickness of the container wall, it has been found that the same layers are surely continuous with each other. Was. That is, even if the pinch-off joint is formed in a tapered shape and the same layers are made to be continuous with each other, the pinch-off joint can be actually made continuous only when the joint is viewed in the longitudinal direction and near the center thereof (that is, at the bottom center). near)
However, there was a problem that the intermediate layer was exposed to the outer surface layer near both ends of the joint (that is, near both sides of the bottom).
That is, the shape A of the split mold of the pinch-off joint of the multilayer blow-molded container having a specific dimension with respect to the thickness of the container wall, the vicinity B of both ends and the center C of the layer cross section of the pinch-off joint formed by this. 5 to 10, when formed in the plane shape of FIG. 5, as described in the above-mentioned publication, the intermediate layer 1 extends over the entire longitudinal direction of the joint portion of the center C and both ends B. Is exposed to the outer surface layer 2, but when formed in the V-shaped shape of FIG. 6, the inverted trapezoidal shape of FIG. 7, and the semicircular shape of FIG. 3, the same layer is continuous with each other, but the intermediate layer 1
Is exposed to the outer surface layer 2, and conversely, when formed in the rectangular shape in FIG. 9 and the trapezoidal shape in FIG. It was found that the same layers were continuous over the entire joint. The reason has not been fully elucidated yet, but the inventor
The reason for this is that when the pinch-off joint is sandwiched by the split mold and the parison is expanded in the split mold, the expansion force near the center of the joint (that is, near the center of the container bottom) is mainly orthogonal to the longitudinal direction of the joint. In this case, the pinching force can be appropriately and uniformly applied to the joint portion, whereas the vicinity of both ends of the joint portion (that is, the vicinity of both ends of the container bottom) can be increased even if the expansion force is along the longitudinal direction of the joint portion. Because it acts strongly and its holding force cannot be maintained properly compared to the vicinity of the center and becomes uneven, in the conventional tapered split mold, the outer surface layer in contact with the split mold is pulled quickly or strongly and becomes tapered. The area near the top becomes thinner, and the intermediate layer may be exposed from the thinner outer surface layer.In contrast, when the sheet is sandwiched by a wide-bottom split mold such as a rectangular or trapezoidal shape, the same applies. Even if both ends of the joint receive expansion force, Since sufficient outer surface layer is confined within the can split mold, it maintains its thickness, the intermediate layer is considered that it would be to prevent the exposed from the outer surface layer. From the knowledge based on this follow-up experiment, according to the conventional technology described in the above publication, for example, polyolefin / barrier resin /
Even in a container having a preferable combination of oxygen barrier property and moisture resistance with a multilayer structure composed of polyolefin, each same layer in these laminates cannot be completely continuous at the pinch-off joint at the bottom of the container. Therefore, it cannot be avoided that the oxygen barrier property and the moisture resistance at the discontinuous portion are lost, and the joint is peeled off by a drop impact or the like.

Further, the above-mentioned Patent Application Publication No. 59-1152 is disclosed.
No. 34, the multilayer container described in FIG. 1 is a container in which a pinch-off portion is formed with divergent ribs that incline so as to expand from a base end toward a front end,
According to an experiment performed by the inventor, the shape A of the split mold of the pinch-off joint of the multilayer blow-molded container having a specific size with respect to the thickness of the container wall, and the cross-section of the layer of the pinch-off joint formed by this method. As shown in FIG. 10, the vicinity of both ends B and the vicinity of the center C are formed into a trapezoidal shape as shown in FIG. Turned out to be continuous. However, in this trapezoidal pinch-off joint container, as described above, the pinch-off portion where the width of the protruding distal end D2 is larger than the width D1 of the proximal end forms a rib that expands from the proximal end to the distal end. Since the container is made of a knife, the tip D of the protruding portion has a knife edge, which is not only easy to be caught, but also has a problem that the protruding tip is bent because the base D has a narrow and narrow width. Dust easily adheres near the end,
There is a problem that it is difficult to remove the dirt. Further, in processing, extra resin material is required as much as the tip protrudes divergently, and it is difficult to process the pinch-off joint of the mold, and when the mold is opened, the resin is set in the rib recess. There are problems such as easy retention.

[0007]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a plastic parison having an inner surface layer made of polyolefin, an outer surface layer made of polyolefin,
And a multilayer comprising at least three interlayers of saponified ethylene-vinyl acetate copolymer, acrylonitrile-acrylic acid copolymer or polyamide having an ethylene content of 25 to 75 mol% and a saponification degree of at least 93%. In a plastic container comprising a molded container wall and having a joint formed by pinch-off and blow molding of the parison at the bottom, the joint may be a container bottom wall.
Forming a projecting portion does not protrude et outwards and projecting shaped portion protruding height H of the width D2 of the width D1 and the protruding end portion of the narrowed portion in the vicinity of the projecting base of the diaphragm portion container wall after the molding For the wall thickness t, Wherein the joint comprises a joint in which each of the three identical layers is substantially continuous in plane.

Here, the joint formed by pinch-off and blow molding of the parison of the present invention forms a protruding portion which does not project outward from the bottom wall of the container, as shown in FIG. That is, the joint portion in the present invention is formed to have substantially the same height as the thickness of the container bottom wall, and the thickness t of the narrowed portion container wall after molding is greater than the thickness of the container bottom wall. That is, it is narrowed down by H. Also, the width D1 of the narrowed portion near the protruding base and the width D2 of the protruding tip portion
The optimum condition is about 0.3 t to t with respect to the wall thickness t of the narrowed portion container wall after molding, and when the thickness is about 0.25 t or less, excessive narrowing occurs. It is considered that the reason is that the container wall is in a molten state at the time of joining, so that a sufficient drawing effect cannot be obtained unless a certain amount of drawing is applied. It is considered that the conditions of the projecting height H and the widths D1 and D2 with respect to the container wall thickness t of the throttle portion also affect the throttle effect similarly. When there is no adhesiveness between the polymer layers of the inner surface layer, the intermediate layer and the outer surface layer in the parison, a blend containing these two polymers is placed between two adjacent layers. The layers can be provided as adhesives to improve the peel strength between the layers.

[0009]

According to the present invention, the projecting height H of the projecting portion is determined by the thickness t of the narrowed portion container wall after molding. And the width D1 of the throttle portion near the protruding base and the width D2 of the protruding tip are As shown in FIG. 2, a multilayer blow-molded container including at least three layers of an inner surface layer, an intermediate layer, and an outer surface layer is formed at a bottom portion thereof. The pinch-off joint at the bottom of the container
In a conventional tapered pinch-off joint, a protruding portion which does not protrude outward from the wall is formed and the width of the protruding portion is within a specific range with respect to the wall thickness t of the constricted portion container wall. 8
As a result, a joint portion in which the same layer was completely adhered to the whole was not obtained, but the same layers constituting the container wall were substantially completely continuous on the entire joint portion. There is an effect that a multi-layer container can be obtained. Therefore, the inner and outer surface layers may be composed of polyethylene or the like having excellent moisture resistance, water impermeability, and toughness, and the intermediate layer may be composed of a gas barrier resin which is weak to high humidity conditions but usually has excellent oxygen barrier properties. For example, in the entire area of the pinch-off joint, each of the same layers is continuous on the surface substantially in the same manner as the surrounding container wall, synergistically exhibiting the unique characteristics of each layer, and oxygen,
Shows excellent barrier properties against various gases such as water vapor and carbon dioxide, and various liquids such as water, organic liquids, ammonia water, hydrochloric acid, etc. Furthermore, the joint is formed thicker than the entire vessel wall. In other words, the strength is stable, and there is an effect of having excellent strength or peeling resistance enough to withstand the impact of falling even when the contents are filled. Further, as described above, the pinch-off joint of the conventional container described in Japanese Patent Application Laid-Open No. Sho 59-115234 is a container in which a divergent rib is formed so as to incline so as to expand from a base end toward a distal end. Therefore, as shown in FIG. 1, not only the width D2 of the protruding distal end portion becomes a knife edge and there is a danger that the protruding portion comes into contact with surrounding objects and is caught, but also the protruding portion is formed around the narrow base end portion. bends there is a risk, also there is hardly take easily the dirt narrow portion of the proximal end portion dust adheres reservoir problem, further processing on the protruding joint from the container bottom wall
If there is a problem that must be raised to the bottom
Both of them have a problem that the resin material cost of the outer layer portion which does not become the outer wall of the container only becomes divergent, but the pinch-off joint of the present invention has a container bottom wall as shown in FIG. throughout formed in rectangular diameter, vessel bottom
Since the container does not protrude outward from the wall , raise the container bottom
Even without doing this, there is no problem that the container sits well, the protruding tip does not catch on surrounding objects, the protruding portion does not bend, and there is no problem that dust adheres to the base end,
This has the effect of solving the problems of the conventional device.

[0010]

In the present invention, the inner and outer surface layers are made of polyethylene, isotactic polypropylene, ethylene-propylene copolymer, polybutene-1, polypentene-1 or the like having excellent moisture resistance, water impermeability and toughness. An ethylene-vinyl acetate copolymer saponified product having an ethylene content of 25 to 75 mol% and a saponification degree of at least 93%, which has an excellent oxygen barrier property, wherein the intermediate layer has an excellent oxygen barrier property, and an acrylonitrile-acrylic material. The multilayer blow-molded container of the present invention can completely protect the contents from intrusion and leakage of moisture and oxygen, and furthermore, the joint can be formed from an acid copolymer or a polyamide. Since the entire wall is formed in a rectangular shape with substantially the same thickness as the container wall, the container is stable in terms of strength. As the oxygen barrier resin for the intermediate layer, various polyamides such as nylon 6, nylon 6.6, and nylon 12 can be used in addition to the saponified ethylene-vinyl acetate copolymer and the acrylonitrile-acrylic acid copolymer. When there is no adhesiveness between these polymer layers, a carbonyl group-containing polymer is blended in at least one of the adjacent polymer layers in an amount of 0.5 to 15% by weight, or as described above. Between two layers adjacent to each other
By providing a blend layer containing these two polymers as an adhesive, the peel strength between the respective layers can be improved.

The blow molding process will be described with reference to FIGS. 3 and 4. A multilayer molten resin flow composed of a plurality of kinds of polymers supplied by being heated and melted by a plurality of extruders is applied to an annular resin passage 5 of a die 4. , And is melt-extruded into a multi-layer parison 6. A pair of split dies 7 and 8 are provided around the extruded parison 6 so as to be able to reciprocate. When the pair of split molds 7 and 8 are matched, spaces 9 and 10 which match the outer shape of the container are provided therein.
In the fusing portions 11 and 12 for holding and fusing the parison when the molds are matched, a concave groove 13 having a rectangular cross section protruding in the thickness direction with respect to the narrowing portion container wall near the protruding base is formed. I have. The shape and dimensions of the concave groove 13 are determined according to the present invention.
In the case of the container, it is set so as to coincide with the protruding portion at the joint portion of the blow molded container in FIG. In FIG. 3, when the parison 6 having a multilayer structure is extruded to a predetermined size, the pair of split dies 7 and 8 move in the alignment direction in the arrow direction, and as shown in FIG. Is sandwiched between the fusing sections 11 and 12 and is blown, and at the same time, compressed air is blown into the inside of the parison through a compressed air blowing port 14 to form a blow molded container 15. At this time, in the case of the present invention, a rectangular projection 16 is formed at the joint of the blow-molded container 15 from the container bottom wall corresponding to the concave groove 13 formed in the fusing portion of the split molds 7 and 8. It will be formed without protruding .

[0012]

[Molding example] For inner and outer surface layers, the density (JIS-K
−6760) is 0.949 g / cm ³ , and the melt flow index (JIS-K-6760) is 0.30 g / 1.
0 min high-density polyethylene of 99 wt%, 1 wt% of titanium oxide (IV) (color mixture of anatase type and rutile type in a 1: 1 weight ratio) as a colorant, density (ASTM-D -1505)
Is 1.188 g / cm ³ and the melt flow index (ASTM-D-1238) is 1.30 g / 10 mi.
n, a saponified ethylene-vinyl acetate copolymer having an ethylene content of 32 mol% and a saponification degree of 95% or more at 110 ° C.
For 240 minutes. For the adhesive layer between the inner and outer surface layers and the intermediate layer, the density (A
STM-D-1505) was 0.901 g / cm ³ , and melt flow index (ASTM-D-1238) was 1.10 g / 10 min, 97% by weight of an adhesive modified polyethylene having 5 mol% of carboxyl groups introduced thereinto. 3% by weight of di-tert. A mixture of butyl-p-cresol was used for the inner and outer surface layers, with a screw diameter of 35 mm and a screw length of 800 m.
m, a screw diameter of 30 mm for the intermediate layer, a screw length of 650 mm, an extruder for the inner and outer surface layers having a screw diameter of 30 mm and a screw length of 650 mm for the adhesive layer, an extruder for the intermediate layer, and an extruder for the adhesive layer; The co-extruder in which the extruder for the intermediate layer is connected to the five-layer five-layer die for co-extrusion is co-extruded under the temperature conditions described below, whereby the outermost layer and the innermost layer are the high-density polyethylene, and the intermediate layer is A saponified vinyl copolymer, a parison having a symmetrical five-layered laminated structure in which these two layers were bonded with the above-mentioned adhesively modified polyethylene layer, was produced and subjected to bottle molding. The temperature conditions of the extruder are as follows: the cylinder rear temperature is 160 ° C. and the cylinder front temperature is 180 ° C. for the inner and outer surface layer extruders, and the cylinder rear temperature is 1 ° C. for the intermediate layer extruder.
85 ° C, cylinder front temperature 200 ° C, in the extruder for the adhesive layer, cylinder rear temperature 165 ° C, cylinder front temperature 185 ° C, die temperature of three-layer five-layer five-layer die is 190 ° C.
Met. The mold used for the molding was a cylinder having a diameter of 40 mm, a height of 100 mm, and an inner volume of 100 cc and having a raised bottom. The mold temperature was 15 ° C.

In the embodiment shown in FIG. 2, the width D1 of the narrowed portion near the base of the projection and the distal end portion (ie, the spread width) D2 of the narrowed portion are equal to the thickness t = 1.5 mm of the wall of the narrowed portion.
1 = D2 = 1.5 mm, protrusion height H = 1.0 mm, and a container having a protrusion rising angle θ = 90 ° was formed. Similarly, the same layers were continuously connected to each other over the entire pinch-off joint. A container was obtained. The continuous state at these joints is
On the surface orthogonal to the longitudinal direction of the joint, cut at many points over the entire joint, the inner and outer surface layers are colored by a coloring agent mixed with the material, the intermediate layer is each layer by a polarizing microscope and a phase contrast microscope, Was confirmed in a continuous state. Further, these containers were cut into 10 equal parts in the horizontal direction, and the inner and outer surface layers that were colored, the intermediate layer measured using the same microscope as described above, and the thickness of the adhesive layer appearing between the layers were determined. As a result of the measurement, the average ratio of the thickness of each layer was as follows: outer surface layer: adhesive layer:
Intermediate layer: adhesive layer: inner surface layer = 40: 5: 10:
5: 40. The average value of the weight of the container was 14 g. From the results of molding under various conditions, It was possible to obtain the knowledge that an optimum continuous state of the joint portion can be obtained under the conditions of (1) and (2).

In the multilayer blow-molded container of the present invention, since the same layers are continuous on the entire surface of the pinch-off joint substantially in the same manner as the surrounding container wall, the unique characteristics of each layer are synergistically exhibited. It has excellent barrier properties to various gases such as oxygen, water vapor, carbon gas, and various liquids such as water, organic liquid, ammonia water, and hydrochloric acid. It has excellent strength or peel resistance enough to withstand. Due to this property, the multilayer blow-molded container of the present invention has various contents, especially liquid, creamy, pasty foods, cosmetics, pharmaceuticals, inks,
It is excellent and effective for preserving a developer, various organic solvents, inorganic and organic chemicals, liquid fuel and the like for a relatively long period of time.

Comparative Example 1 A container obtained by the method described in the above-mentioned molding example (hereinafter referred to as the container of the present invention) was used for comparison with a conventional pinch-off mold under the same conditions as in the above-mentioned molding example. A multilayer container is formed, and the width D1 of the narrowed portion in the vicinity of the protruding base is 1.5 mm and the height H is 1.0 mm. The inside of each of the molded container (hereinafter, referred to as a conventional container) and the single-layer container of the same shape molded with only the high-density polyethylene described in the molding example (hereinafter, referred to as a coalbed container) is filled with helium gas. After sufficient replacement, the mouth was thermally welded with an aluminum foil having a thickness of 30 microns. Thereafter, it was left at 25 ° C. in an atmosphere of oxygen, carbon dioxide and water vapor. At this time, the amounts of oxygen, carbon dioxide, and water vapor entering each container were measured, and the values in Table 1 below were obtained.

[Table 1]

Comparative Example 2 The three types of containers examined in Comparative Example 1 were filled with gasoline for automobiles, paint thinner, 35% hydrochloric acid and 28% aqueous ammonia, and sealed with a predetermined cap. Thereafter, the sample was allowed to stand in an atmosphere at 25 ° C. and a humidity of 75%, and the change in weight was measured. As a result, the values shown in Table 2 below were obtained.

[Table 2]

[Brief description of the drawings]

FIG. 1 is an enlarged longitudinal sectional view showing a section of a pinch-off joint of a conventional container.

FIG. 2 is an enlarged longitudinal sectional view showing an essential part of an embodiment of the container of the present invention.

FIG. 3 is a schematic explanatory view showing a state in which a split mold for explaining a multilayer blow molding method is open.

FIG. 4 is a schematic explanatory view showing a state in which a split mold for explaining a multilayer blow molding method is closed.

FIG. 5 is a cross-sectional view schematically showing a cross section of a pinch-off joint of a conventional container together with a split shape of a fusing portion.

FIG. 6 is a cross-sectional view schematically showing a cross section of a pinch-off joint of a conventional container together with a split shape of a fusing section.

FIG. 7 is a cross-sectional view typically showing a cross section of a pinch-off joint of a conventional container together with a split shape of a fusing portion.

FIG. 8 is a cross-sectional view schematically showing a cross-section of a pinch-off joint of a conventional container together with a split shape of a fusing portion.

FIG. 9 is a cross-sectional view schematically showing the cross section of the pinch-off joint of the container of the present invention together with the split shape of the fusing portion.

FIG. 10 is a cross-sectional view schematically showing a cross section of a pinch-off joint of a conventional container together with a split shape of a fusing portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Middle layer 2 ... Outer surface layer 3 ... Inner surface layer 4 ... Die 6 ... Parison 7, 8 ... Split mold 11, 12 ... Fusing part 13 ... Concave groove 16: Projection

Claims (1)

(57) [Claims] 1. The container wall of a plastic tubular parison comprises an inner surface layer made of polyolefin, an outer surface layer made of polyolefin, and an ethylene content of 25 to 75.
A multi-layered container wall comprising at least three intermediate layers consisting of saponified ethylene-vinyl acetate copolymer, acrylonitrile-acrylic acid copolymer, or polyamide, wherein the saponification degree is at least 93% by mol%, In a plastic container provided with a joint formed by pinch-off and blow molding of the parison at the bottom, the joint forms a protrusion that does not protrude outward from the container bottom wall , and the protrusion height of the protrusion is H, the width D1 of the narrowed portion near the protruding base portion and the width D2 of the protruding tip portion are determined by the thickness t of the narrowed portion container wall after molding. Wherein the joint comprises a joint in which the same three layers are substantially continuous in plane.